Omeprazole (trade name Prilosec), a specific inhibitor of the gastric proton pump (H.sup.+ +K.sup.+)-ATPase, can be prepared by coupling 2-chloromethyl-3,5-dimethyl-4-methoxypyridine and 5-methoxy-2-mercaptobenzimidazole, followed by oxidation. 2-Chloromethyl-3,5-dimethyl-4-methoxypyridine is readily obtainable by chlorination of 2-hydroxymethyl-3,5-dimethyl-4-methoxypyridine, which, in turn, can be prepared from 2-cyano-3,5-dimethyl-4-methoxypyridine, i.e., compound 1 shown in Scheme A below, by procedures well known in the art (see, e.g., European Patent Application 369,208).
Conventional methods of preparing 2-hydroxymethyl-3,5-dimethyl-4-methoxypyridine involve using either N-oxide or nitropyridine as an intermediate. E.g., see U.S. Pat. No. 4,255,431 and European Patent Application 369,208. Both N-oxide and nitropyridine have been reported to be carcinogenic.